Program Mencari Bilangan Prima

#include <iostream.h>
void main()
{
long a,b;
cout<<"Program mencari bilangan prima"<<endl<<endl;
cout<<"Masukan batas bilangan pencarian bilangan prima : ";
cin>>b;
for (a=2;a<b;a++)
{if((a%2!=0)&&(a%3!=0)&&(a%5!=0)&&(a%7!=0)||(a==2)||(a==3)||(a==5)||(a==7))
cout<<a<<endl;}
}